Installing a Drimaster Heat PIV system

*** NOTE:  As this site is actually our travel blog, and this page is really popular, I’ve relocated this content and more to a new site dedicated to this topic HERE (  )  ***  Please look there for more updates, more information and feel free to add your comments there instead.  Any comments posted here will be copied to the new page as that should have more hits *****

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  • Update from October 2013 at the bottom.
  • Update from March 2014 from me and someone else (Darren) at bottom
  • Update from end October 2014 (pics of final install)
  • Update November 2015:  Ours still going well 🙂 – and just noticed they are selling one with a free temp/humidity meter (so £10 freebie) – see right…..

Please note this is a genuine blog post, and not a sales advert or “info-mercial” 🙂

Our house is a 1933 detached house, with cavity walls without insulation, and modern-ish double glazing.  We moved in mid June 2012.  We noticed a slight issue with condensation in that the bedroom windows get wet overnight, and we’ve noticed a couple of small patches of mould on cold external walls.  Its quite a minor issue for us, but pretty much down to the modern way of living – warmer air with central heating, and not as much ventilation due to double glazing; bricked up fire places; and roof insulation.  (using and venting the fireplaces is next!).  Update:  Whilst decorating, it has become obvious the previous owners covered up mould issues they had, so the mould problem would clearly get a lot worse)


If we leave the bedroom windows open a notch, there is a lot less condensation which sort of proves the point.  For more information on the causes of condensation see

Anyhow, we all know mould/damp is a pain, and we thought we’d be proactive about it, and thus try and avoid any future problems (like mould behind wardrobes etc) – especially as we’ve just started decorating the new house.

A couple of “internet friends” on a plastic car forum mentioned and that they had a PIV system installed from them, and had astounding results.  Environvent seem to be a consultancy/installer and not really suitable for DIYers – and hence the cost is fairly high.  But, the first-hand results I heard were positive.  So I started looking for alternative PIV systems…

What is a PIV system?

Well, its a “Positive Input Ventilation” system which basically is a system which increases air pressure inside a house which forces older/wetter air out of the house and thus prevents condensation.  Thats the theory, and to be fair I’m not entirely convinced it isn’t a snake-oil product!  The forum threads and give both sides of the story – many people saying the systems are superb, and a few saying they are not.  Interestingly, the miricle stories seem to be from owners, and the negative comments seem to be from the theorists.

I came across Nuaire Drimaster products and as these can be bought as DIY installations at reasonable cost, I thought it was worth a punt…


Nuaire Drimaster Heat

I opted for a Nuaire Drimaster Heat ( ) .  This is a loft-based PIV system with a single loft based unit with an outlet on the landing.  This system (apparently) does: –

  • Programmable speed for small or up to 5 bed houses.
  • Clever automatic heat recovery to use “solar gain” if the sun is warming the loft space
  • Auto summer shut-down
  • Air heater if loft air is cold

The air heater is a 500w heater which makes the air warmer if the air in the loft is cold.  This is for “our” comfort rather than any anti condensation functionality as it just prevents cold draughts.

Another benefit is that as the air is sucked out of the loft, it will actually force air movement and refresh in the loft space which of course will help with loft ventilation.

Nuaire have been established for 20 or so years; sell internationally, and also sell commercial grade products.  This inspires confidence in the product and company as I doubt they’d be around so long if it were snakeoil…  The product feels well made, and if nothing else, it is well engineered!  It comes with a 5 year warrantee.

Possible issues

As the air is pulled from the loft, when it is very cold, then very cold air will be blown into the house.  This is minimised with the heater, but of course it is still sending in cold air.  Our stairs/hall are coldish anyway so not overly concerned, and I’m guessing this is better than open windows in each room anyway.  Time will tell.


The kit comes with everything you need, bar some suitable cables, but I’ve opted to wire it slightly differently.  I’ll use 2 double-pole fused isolators, one for the entire unit, and one just for the air heaterSam_1929.  This will mean it complies with regs having an isolator, but also I can enable/disable the heater if I desire without affecting system functionality. (if I find a spur-timer cheap enough, then I’ll install one for the heater to prevent the heater running overnight).

The rest of the install looks a doddle….!

  1. Cut a 225mm hole in the loft ceiling suitable for the output vent.
  2. Mount the brackets on suitable joists
  3. Fix unit to brackets
  4. Connect and seal ducting tube
  5. Cable up as necessary

Sam_1931I connected it to a fused spur off the lighting circuit as this was more accessible in the loft and isn’t as naughty as it sounds as, for example, shower extractor fans and shaver points are run off the lighting circuit.  The Drimaster Heat is fused at 3A but pulls a maximum of just over 500W, and as the lighting circuit is 6A and all our lights are low power, there is plenty of capacity.

Once installed, we set it to speed 4 (of 6) which is the right speed for our size house, and this seems to pull a constant 16W to run the fan which equates to 4p per day (excluding heater).   Pending success or otherwise, I may reduce speed to 3.  (4 = 40 litres of air per minute)

All that can be seen in the landing is a fairly discreet and flat vent, and the isolating switches.  Once the celing and landing is finished and decorated it will blend in fairly well.

In the loft, the grey bit (between the green bit and the flexy pipe) is the heater, and clearly I’ve ensured there isn’t any insulation touching or close the heater enclosure, even though its not that higjh powered or likely to be a problem.

Overall, a nice simple install, and now see if it works…..



Does it work?

The system works, and you can feel a nice amount of air movement.  The fan is very quiet and completely non intrusive.  We installed it as per the instructions and do not have a noticable draught.

After a few hours

Placebo effect or not, the upstairs landing definatley felt fresher, so if nothing else, the system moves more air around!  The landing does feel a bit cooler, but not colder….   We’ve closed half of the upstairs windows and will see how things look in the morning…

First day

Well, the upstairs landing is definately cooler and fresher.  I guess a thermometer would show it being colder, but it doesn’t feel cold.  Weird, but guess its the humidity change.  Overnight we closed 1/2 the bedroom windows, and in the morning the windows were still a bit condensated 🙁  So no magic solution after the first night.

5 days later

After being out for a couple of days, we came back and the hall/landing was still fresh.  Maybe we need to turn the speed down a bit!  But, we have closed all windows upstairs (and we don’t have trickle vents).  As such, the bedrooms are definately much warmer.  The first night back we slept with the windows fully closed which would normally mean wet windows, but on the first night back (day 5) the windows had a lght mist only on the bottom 1/4 of the window.  And by light mist, I mean as if you just simply breathed on the glass.   It was however a warm night 🙂

The next day it was 0’C outside, and with windows closed would normally result in very wet/condensated windows.  However, in the morning the windows were 99% clear of any misting or condensation. maybe 1cm high light mist at the bottom.

Bizzarely I’m still not convinced lol!  But the last 2 days have been mightily impressive.  Just need to monitor to ensure it is working as it still feels too good to be true.

The cooler landing isn’t an issue as the bedrooms are definately warmer, and we’ve opted not to use the built-in air heater just to see how it goes.

So, 5 days in, looking good….

Update 30 October 2013

Well there has been a lot of interest on this page, and a fair few people asking how it has gone and if it works, so thought I’d do an update.

Its interesting as, as you know, I’m a sceptic 🙂  We have at last decorated the landing so the system is now much more discreet.  Its been on 24×7 and the heater (which I’ve got on a separate switch) was only on during the very cold winter.

Its hard to say for 100% certainty if it works as no two nights are the same humidity or internal/external temperature, so the scientist in me hasn’t yet proved it.  A mild October doesn’t help comparison.  BUT – since installation we have NOT had to wipe any windows down at all.  Last night (Wet and 5′ outside), we have 2-3cm of LIGHT misting at the bottom of the window.  (prior to installation it was thick misting all over that would run off and the sort you could wet a towel on – but we’ve had nothing like that).

The mould we did have (fresh and small black dots) has gone or gone grey and easily wipes off.

We have checked, and there is NO mould behind any furniture or wardrobes etc.

BUT – we’ve also learned about condensation and made other changes which all help:-

  • We fitted a powerful shower extractor fan (vented externally), and leave the bathroom window open for a few mins after a shower, and close the bathroom door.  We also have the temp a bit lower.
  • We’ve had the house re-roofed (not related!) and this meant a new breathable felt membrane and also meant we could add insulation to otherwise impossible to get at areas in the corners of the rooms.
  • We leave windows on “night” settings in rooms we have the heating on low (e.g. guest room)
  • We use the cooker extractor fan (vented externally) when cooking
  • We have had a log-burner installed (which when used sucks moist air from living area and uses it thus removing moisture)
  • We have installed vents in other chimneys that were bricked up
  • We leave the bedroom door slightly ajar most of the time (though we close when guests stay and its still okay)

So the Nuaire Drimaster is only part of the changes we’ve made – and hence hard to say if it does the job by itself.  Oh – and we altered the default program so it goes into “heat recovery mode” when loft is 18′ or more which is lower than normal, and set the heater to only come on <14′ over winter, which suits our install.

SO – the bottom line is – I can’t 100% prove it, but from a week after installing, we have not had to wipe down any windows or had any condensation issues……..

Would I buy and install again – yes.

Update March 2014

After Darren took the time to post in the comments section, completely unsolicited, I thought I would also give an update.

After decorating we found evidence that mould had been covered up and bodged by previous owners.  However, after decorating and with this system still running, we have had NO mould appear, walls dry, and windows only “very minor” condensation on a cold night – and that is with windows locked closed (so minor, windows not wiped or opened).

Over winter the loft air is cool so the heater takes the chill off but (of course) uses power to run – 500W, so max 12kwh a day, £1.50 max?  Of course it isn’t on full all the time (automatic), but maybe £20-30 a month over cold winter months.  Still cheaper than fixing mould!  And of course the heater is for OUR benefit, not to help with condensation.  The reverse, when the sun comes out the loft gets hot and we’ve tuned the Nuaire to go into “high speed” mode when loft is >18′ – so when sun on roof we get “free” heat blown out.  Also as air is “better” the heating is probably lower than it used to be for the same comfort.

We’ve decorated the landing now so the unit can hardly be seen and its just forgotten about and it quietly gets on with the job.  Still happy with it, and it still works….

From Darren (see comments):  “Just wanted to say thanks to Ryan for this blog, it helped persuade me to purchase a drymaster heat which has been running since early December. My house suffered really bad with surface condensation on windows, walls, behind furniture, mold etc. Thought I had rising damp at one point but after research and reading this blog heard about PIV. All I can say is that this system has totally cured our problem. Since installing I have not ONCE had to wipe down windows at all. This is amazing as our windows were normally saturated every morning in the winter months. I cleaned all the mold off the ceilings and walls after a week of installing the unit and to my amazement it has not come back whatsoever. The house feels fresher as all the stale air is constantly pushed out of the house so it is just a nicer environment. I will mention that you will notice the landing will be a bit colder due to the fresh air being pumped into the house, I could turn on the heater but have not felt the need so far. For people asking about settings it depends on your house, installation and severity of problem, I have a 4 bed house and suffered terribly, I initially had it on setting 4 but have recently turned it down to 3 and it is still working fine. I have also been able to turn down the heating thermostat as its so much quicker to heat the house due to much lower moisture.

I got a sparky to fit it and it was real simple for him. I purchased a heavy duty chain and hook from screw fix for £10 and hung mine from the rafters, it really works well and means no vibration. I would recommend anyone buying one to do the same. I also like Ryan run the heater off a different switch in my airing cupboard, that way if I need the heater on its simple to do without climbing into the loft.

I really can not say enough good about this system and for anyone wondering if it really works, it really does. Would I buy one again, 100%

Update October 2014

So, its 30 October 2014 and I’ve just turned the “heater” part back on as its getting cooler.  The heater has been on for just over a week and using an extra couple of units a day, but nothing too much.  But the system has been on all summer and still, house is mould free and even checking behind units its fine. 

I thought I’d better upload a pic of the final install as the picture above makes my house look like a building site!  It was, but once decorated the unit is very discreet.  The lighting is poor and the photo makes it look more obtrusive than it is its the early morning shadows- in fact its barely noticeable and visitors seldom see it, and as its quiet they don’t hear it.


Please note, Amazon is a good source of the Drimaster, but they appear to have the same item listed numerous times and at different prices.

(Please note, for openness, like all Amazon ads on this site I get a small commission if you buy from them.  For the Drimaster, its £7.  You pay the same to Amazon and do not pay any extra.  Thanks to the people who have bought via this site – each purchase buys me & the missus a beer!)

TOP TIP (painting over old mould)

When redecorating we had one corner that use to be very mouldy, and previous owners clearly bodged it which meant that I could not paint over it – standard emulsion would just not dry.  No idea what on earth they did!

So, another top-tip from me is to buy some Zinsser BIN (B-I-N).  This is a special paint which is expensive, but it does what it says on the tin.  Basically, you roller-paint it over any problem areas (like mould, old water damage, rust marks, rusty nails embedded in wall, old chemicals/gloss paint etc) – and go for a cuppa. After 45 mins its dry and you can emulsion over it as normal (!).  Yeah – really!  It is a must-have for every old house.  I’d recommend a cheap foam roller set from Poundland as the roller will need binning after use.

Where I’ve used this, the emulsion paint has been perfect, and no marks have come through.

76 thoughts on “Installing a Drimaster Heat PIV system”

  1. Hi. Just wondering after 6 months what your impression is of the Drimaster now? We are thinking of installing one in our solid stone walled house that suffers with inevitable damp issues. Any feedback would be welcome. Thanks.

  2. just wanted to share my experience fitting a Nuaire Flatmaster with everyone, this could happen when fitting a Nuaire Drimaster too!

    I had been quoted £980.00 + VAT from Envirovent and £780.00 + VAT from a Nuaire fitting company. Both prices sounded reasonable but I did a bit of research and found I could buy a Flatmaster on Google with a heater for £320.00 + VAT so I went ahead and purchased it.

    The unit arrived the next day, I was then shocked by the complexity of fitting it, which needed to be sighted in a central location and an input vent cut through the wall and various ducting installed.

    This was too much for me, so I called Nuaire and they recommended an installation service but he wanted £600!

    The solution was obvious call in a local contractor; I looked on Google and found a PCA approved company who was a damp and condensation specialist.

    They sent around Miguel (with an invoice of £400.00 + VAT) he sat on the floor and opened the box and read the instructions then proceeded to cut a hole through my wall to install the inlet. The mess was so bad, dust everywhere! He said it was the only way. He then spent time installing the ducting and finally wired in the unit to the main ring. I asked him if he was qualified and said we are Part P approved.

    He blew all the MCBs and I could smell burning at that point I showed Miguel the door with his unpaid invoice.

    I contacted Nuaire again who gave me phone number who I called, they fixed the wiring and sorted the fan.

    They told me installers should be BPEC this is an industry regulation relating to ventilation products.

    The summary of the story is always use a proper company or it will lead to problems like I had and even invalidating your insurance by having an unsafe unit fitted.

  3. Hello to everyone interested in this post, we are west Yorkshire based specialist remedial company( who supply and install the Nuaire Drimaster Heat and other Nuaire Products, i can only praise this unit as this works with great performance where condensation has become problematic, we have been installing this unit over the last 4 years and have never had one complaint or criticism.If you are in two minds if to install this in your property i can only advise to go ahead and you will not be disappointed, please use a reputable installer that fully understands the product and also understands the property and severity of the condensation problem so the unit can be set up to deliver its best performance,if you live in the Yorkshire or surrounding areas and require further advice or a quotation for installation please do not hesitate to contact us further.

    Steve Pearce

    1. NOTE FROM DYD: Thanks for your comments Steve – but as you didn’t have the courtesy to ask first I have deleted reference to your company as this is not for free advertising for any old company who spams my blog. I’ve left your comments though as they may be useful to readers

      1. Like your idea about wiring the heater separate. Was this easy to do as the wiring diagram for the unit looks pre-wired.

        1. Hi
          It was trivial – the heater is pretty much entirely separate – it can be added separately and is fully independent from the main unit – the thermostat and control is in the heater, not the drimaster.
          So I had

          power----->switch 1---> Drimaster
                             \--> Switch 2 --> Heater

          So switch 1 isolates both, switch 2 just heater.

          Hope this helps

      2. Sorry to all for making reference to my company name no hurt or malice intended, sorry Ryan and mell



    2. I know this post is 7 yrs old but need an installation of a Nuaire piv please contact me Julie . Bennett 3 @ please

      1. Hi
        I’m only a DIYer who did mine – not able to help 🙁
        But, 7yrs is it – blimey. It still works perfectly and we’ve had no issues since install
        Good luck

  4. Hi Ryan

    i just installed the unit today the way i wired the unit is on two separate fuse spurs one for the main unit and one for the heater. Son one fuse spur switches the main unit on/off and the other one switches the heater on/off. Can you please confirm this is OK??

    1. I am not qualified to give you advice – this page just shows how I did it. I did it differently – my heater fused spur is off the main fused spur. Thus the main switch turns and isolates everything; and the second switch isolates just the heater. Current draw etc taken into account. This is my way – not giving advice nor saying which is better. I am not qualified to advise.

      1. Thanks i spoke to Nuaire today and they confirmed it can be wired both ways. One more thing Ryan how can i check if my heater is working? there is a red light in the control box which flashes when i switch the heater on. does the red light means the heater is on??


        1. I don’t actually know – I always had the cover on when linked up to the mains! 🙂 Its easy to check if you watch a “power meter” as it’ll drop about 450W when its on!

  5. Really grateful for all of your info Ryan/Mel. I’ve just been quoted £800 to have one of these installed in a three-bed standard terraced house!!! Thanks to you, I’m going to buy a unit myself and have my (fully qualified) electrician install it for me.
    Thanks again from (Fellow Motorhomer) James

  6. I’ve installed a drimaster heat. Could you tell me what settings it should be on please. The upstairs landing is really cold, a lot lot colder than it was before I installed it. I live in a 3 bedroom semi detached house. Thankyou

  7. My son installed a nuaire drimaster heat for me. Could u tell me what settings it should be on plz. It is very cold on my landing. I live in a 3 bedroom semi detached house. Thankyou

    1. I would try setting 3. If any sides of the diffuser are very close to a wall (less than about half a meter) I would also block that side of the diffuser off with the provided sponge blockers, it will then divert the air out of the other sides and should reduce the cold air running down the walls which may be why you are feeling the cold. Just a thought.

  8. Just wanted to say thanks to Ryan for this blog, it helped persuade me to purchase a drymaster heat which has been running since early December. My house suffered really bad with surface condensation on windows, walls, behind furniture, mold etc. Thought I had rising damp at one point but after research and reading this blog heard about PIV. All I can say is that this system has totally cured our problem. Since installing I have not ONCE had to wipe down windows at all. This is amazing as our windows were normally saturated every morning in the winter months. I cleaned all the mold off the ceilings and walls after a week of installing the unit and to my amazement it has not come back whatsoever. The house feels fresher as all the stale air is constantly pushed out of the house so it is just a nicer environment. I will mention that you will notice the landing will be a bit colder due to the fresh air being pumped into the house, I could turn on the heater but have not felt the need so far. For people asking about settings it depends on your house, installation and severity of problem, I have a 4 bed house and suffered terribly, I initially had it on setting 4 but have recently turned it down to 3 and it is still working fine. I have also been able to turn down the heating thermostat as its so much quicker to heat the house due to much lower moisture.

    I got a sparky to fit it and it was real simple for him. I purchased a heavy duty chain and hook from screw fix for £10 and hung mine from the rafters, it really works well and means no vibration. I would recommend anyone buying one to do the same. I also like Ryan run the heater off a different switch in my airing cupboard, that way if I need the heater on its simple to do without climbing into the loft.

    I really can not say enough good about this system and for anyone wondering if it really works, it really does. Would I buy one again, 100%

    1. Hi Darren. Thanks for your comment – really good to hear. We still have a zero issue (even with windows closed) – but as it is a bit of a snake-oil product, I am pleased to hear firsthand that it is helping someone and isn’t just luck. We also tuned our heat recovery settings, so whilst the heater is on when its cold, when the sun is out the heater clicks off and the fan speeds up sucking the heat out of the loft space – and that does help.
      Thanks again for making an effort to post here.

  9. been charged £850 to supply and fit
    what u think?
    how much electric does it consume a year? in pounds?
    i have a big mould and black condensation problem

    1. I’m only another customer, so can’t say as every install is different and may take a while to do depending on access etc. Seems a bit steep though as its <£400 for item and other parts, so £450 labour... Depends how long it takes. Took me probably 3-4 hours? As for how much cost to run, again depends on your settings. My costs are listed in main post.

    1. Thank you for your post – pleased to hear other successes as otherwise “readers” may think I’m just doing an info-mercial!

  10. i had a Drimaster installed about two years ago in my very old stone cottage. We had dreadful mould problems as the walls are three feet thick and very cold. The Drimaster has completely cured the mould and I haven’t had to bleach the walls since installing it. My only query is whether, now that I’ve had central heating installed, we are paying to heat the outside air, since presumably the warm indoor air is being drawn out and cold, dry air being drawn back in. Any comments would be welcome. Thanks.

    1. The system pulls in air from loft/outside and blows it in. Yes, in winter its cool/cold, that’s why I bought the drimaster heat. The warm air inside only escapes via normal holes, its not blown out. If you want to minimise that you need a fully blown heat recovery system. But the Drimaster Heat should be fine, but of course cost to heat the cold air in winter, but cheaper than fixing mould!

  11. Ive the Drimaster Heat but cant work out the heater settings can someone give me some advice on this please. My landing is certainly drier but a lot cooler.I only seem to manage to turn the fan up or down and cant get my head around the settings.
    I fitted the unit about 6 months ago.

    1. There are 2x different settings. One on the behaviour of the unit (see section 12) – for loft heat recovery. Think I went for option 2 or 4 – can’t remember. Read the manual as getting to this program mode is awkward. Also, you can adjust the dial on the board of the heater to the set temperature on the heater. Make sure the heater is working and “on” too – as if “on” the air should be as warm as you want it. (though balance between heat & cost….)

  12. I bought my Drimaster-heat on Amazon for £307, cut the hole, installed the vent, then the unit in the loft as per the instructions, the only difficult bit was getting the flexible tube on to the unit but all in all one afternoon, wired it, tried it, works perfectly (have to have it checked by a qualified sparky now). So, not too difficult to install, there is also a very good video on Youtube which helped me.

  13. After extensive research, due to being cynical that it would work I purchased this unit. We have a 90yr old bungalow with solid walls and suffered with mould in the three bedrooms. Humidity levels were 74 – 77% every morning, Envirovent suggested readings should be 45 – 55% along with their quote of £2000 which is why we went for Nuaire.It has now been installed for a week, I helped the electrician install it so his charge was £100 and took us 5hrs.
    24 hrs after install (on setting 4 which is probably too high for the size of property) the readings had dropped 10% , after five days they have dropped to 53%. The walls affected by mould now have a “powdery” feel to them as they are drying out. Their is a 2cm band of condensation on one of the bedroom windows and that’s it. We’re staggered by the results and has by far exceeded expectations so thanks to this blog and all the comments for advice. We never believed that we would cure it for £400 – as I look out now all the neighbours have their windows open except for us.

    1. Hi Paul
      Thank you for taking the time to reply, I never checked humidity levels to good to her the difference that makes. After 2 years, we are still surprised it works lol – but even today, -2’c outside, windows closed, we just have a 2cm band of condensation which clears quickly. One day this year we had a light dusting of mist over the window (maybe we generated too much moisture overnight lol) – but still never wiped the window.
      Hope this page helped in your research. Best wishes

      1. I bought the digital humidity meter for £3 for our sons room but do move it around as slightly obsessive with checking the readings! As one aspect of the diffuser is within 400mm of the wall I refitted the foam insert. The next day there was damp on one wall (humidity 82%) so removed the insert. Within 30 mins it had dropped by 5% and it was back to dry wall by the next morning, just proves how effective it is. Certainly your blog was a great source of info especially independent wiring of the heater which we haven’t felt the need to use yet despite the below zero temperatures this week. Will it automatically shut off in the summer or do I need to adjust the settings? Are your camping tips as good ??!

        1. lol – yes, camping tips are what this site is about 🙂 So over xmas I duplicated this page and added more info to (copied your comment if that’s okay)

          To answer your question, if the wall is getting damp WITH a drimaster in the room (but with foam insert in) – then wow – that is a problem wall. We need just one drimaster in the landing and it deals with all of the house. Of course, blowing air down the wall will help – but there may be other causes of damp there as that sounds extreme – the outlet in the room should be enough as it should work by pressure, not “blow flow”.

          The heater is thermostat controlled, and will come on and off as necessary – so set correctly the heater will be off during the summer anyway (though mine I can switch off manually). If you don’t have it on, then your wall must be freezing! The PIV is on 24x7x365 even over summer, but its very low power and is happy being left on – and also speeds up if the loft gets hot so to get “free heat” under certain conditions.

  14. We have a 4500 sq ft 3 story house with 26 windows which would have approx 1 inch of condensation on a cold frosty night. We fitted 3 drimasters units 6 weeks ago, 2 of them on the top floor set at 4 and 1 on the 2 nd floor set at 3. The house was originally 2 houses put into 1 big house. I bought a humidity meter and the readings on it can be as high as 83percent, should this not be lower. We would still get condensation approx. 1 inch on very cold nights. The air in the house is fresher and cooler. The 2 drimasters fitted in the top storey use the same roof space which is about 30 ft long and 12 ft wide. Should these drimasters not work better at these settings and why is the humidity still so high. Does it depend on the outside weather conditions, if it is a wet day the humidity inside is higher, is damp air being pulled into the house or does it depend on temperature of the house? Please if someone can help me, should we still get condensation with the drimasters running at the settings stated and the approx. size of the house. If you have any thoughts on these I would really appreciate your comments. Thank you

    1. Hi Linda.

      See for more info as I’ve moved this topic to a dedicated site. I’ve duplicated your comment there.

      Please see the “about us” page, as I am most definitely not an expert on this topic, I’m just some bloke on the internet who has one!
      I would say, 1″ of condensation isn’t bad – we still get maybe 1″ at the bottom of the bedroom windows on some nights. Previously, prior to install, we used to get the entire window “wet” – not just condensation but water running down, so getting to 1″ for us was a success.
      83% humidity does sound high though, and remember the PIV does not dehumidify and should only be part of the solution. So I would say you need to look at HOW the moisture is getting there in the first place and address that. See – as if you are drying clothes over the radiators, and do not extract from the bathroom, then you need to address this first.
      If your loft is damp/leaking or has high humidity, then yes that will be pulled into the house. No one else has mentioned this…. Maybe monitor the loft humidity? We had the house reroofed with a breathable membrane (post PIV install due to roof leaking, not related).
      Sorry I can’t help more

    2. Two fans mounted in the same place can cancel each other out. Its the same if you use two extractor fans in a kitchen at the same time. The drag from the two fans can create a negative pull as they pull against each other. One fan running at higher speed would be much better. I am not a scientist at all but in my years in the building trade I have seen this happen. The first time was a kitchen that had a fan in the window and a ducted cooker hood over the hob. The lady naturally though to put both the fans on at the same time and get double benefit but no, the kitchen was full of condensation. I told her only to use one fan at any time an no condensation. I suppose you could say that was a scientific experiment.

  15. Hi,

    I am thinking of getting a Flatmaster for our 2 bedroom flat. Only place I can install it is in our boiler room. Do you think it’s ok to have the inlet next to the boiler’s exhaust outlet? There is a hole already on the wall that I can put the inlet of the Flat master through.

    Any comments are much appreciated.

    Thank you.

    1. I’m not an expert and don’t pretend to be, so you really should contact Nuaire and ask them for their rules & regulations My personal feeling is not a hope in hell! The flue is there to get rid of toxic gas. Even having a window close is prohibited. Having a suction inlet pulling those fumes in is likely to put you on the Darwin award list.
      Maybe outlet and run ducting to somewhere safer – but please speak to the manufacturers and experts. Gas combustion fumes can easily and quietly kill – so don’t risk it

  16. Can you help I have installed a drimaster about 12 years ago and it has stopped going the transformer box with the green light seems to be flashing and all the red lights are flashing as well nothing seems to be going has the motor gone and do I need to replace the unit

    1. I have just had the same issue, however I have only had mine a matter of months. Did you ever find out what was wrong?

  17. Hi, we have condensation on our bedroom windows. We sleep with the door closed. Would we have to have the vent in our bedroom or would a landing vent still be effective.
    Many thanks,

    1. The way these things work, is *slight* extra pressure and that causes air movement. A single unit, vented on landing, is good enough for 4 bed house. On most doors, closed or not, there are big gaps where air naturally flows. So no, you do not need an outlet in the bedroom – just a single outlet on landing.

      However, if you have an air-tight door then well, that isn’t going to work 🙂

      Also remember I am a single happy customer/user and not an “expert” contact supplier with any questions – but hope the above is useful

  18. Hi Ryan and Mel. Thanks for the detail on the drimaster. I’ve just moved into a 1930’s bungalow which has a condensation problem. Having researched the Nuaire products, I think that this would definitely solve the problem for us. I have one question which I hope you can help with. Our house has an upstairs extension, so very little loft space remains (and certainly not enough for the drimaster). We have a large cupboard in one of the eaves, which I thought could be used, but it would mean that the kit would have to be installed with the output vent and diffuser being aligned horizontally to the machine rather than vertically as is shown in all the photographs I’ve seen. Do you think that this would be ok? I’ve looked at the flatmaster as an alternative but would prefer to avoid the trouble of putting a hole through an external wall. Thanks for your help.
    Best, Frank

    1. Remember I am an owner/user – not an expert.
      But if I read you right, you want the outlet vent horizontally? Personally, I see no issue with that as long as the air comes out it should work. Depends where it is and ensure the room has airflow. Make sure the cupboard has a large volume of air that would otherwise be isolated from the house (e.g. drawing air through eves from outside).
      So in other words, if it is the equivalent of in a loft, vented externally, I don’t see why a horizontal outlet would differ from a vertical one.
      Good luck

      1. Thanks. Your point about having air coming in through the eaves is exactly what I was thinking. Will check this out. Thanks again.

  19. Hi Ryan/Mel, Just a quick question…and many thanks for all your hard work in putting all this info together. If the unit is basically sited in the upstairs loft, is the flow of air just as effectiuve downstairs as upstairs? My problems are mainly downstairs but also a bit upstairs. Many thanks! Pete

    1. hi
      in theory yes they cover the whole house.
      bt condensation is caused by moisture in air so bedrooms usually suffer. so why do you get in downstairs? where is the moisture coming from? cooking, washing, drying clothes, leaky pipe, damp etc…? if so sort that – piv is not a miracle fix all you need o address the cause if you can – then piv will help
      see my site dedicated to this rather than my travel blog lol see
      more info and hints there on addressing getting rid of moisture
      remember I AM NO EXPERT

  20. Hi there. After reading this blog I have also decided to install a nuaire Drimaster, but as my property is rented out I’ve decided to save myself £150 and have the standard drimaster (unheated version). We live in cornwall which doesnt suffer so much from the cold as it does rain and dampness. I too have a 100+ year old cottage with no cavity and mold appears EVERY winter behind sofa’s and in corners of the bedrooms (outside walls) The installer who is fitting it next week said it should be fine as long as they have central heating on you will not feel draft from the fan? Has anyone else opted for the standard unheated version and have any comments on how it make the house feel? As last thing I want is phone calls from tennants saying house is colder!!!

    1. I would opt for the heated version, it does not have to be used but as it can not be retrofitted it will save you hassle if you find it too cold.

  21. Hi l live in a rented house and have a drimaster heat installed by the landlord when it first went in it was freezing only when heating was on full was it bearable, he then had the setting changed lowered fan setting and lowered the heating setting to come on it is now winter and its like having a window open constantly, the hallway struggles to get upto 18oc and when my heatings off falls to 15oc and bellow so cold. Electric its costing £1.50 a day add that to heating costs its so expensive yes its sorted the condensation, but its costing me a fortune in heating and electric and making the house cold its like chucking money down a drain trying to keep the house warm!

    1. hi
      thanks for your comment. I think the fan speed may be too high still. ours is cool but not freezing and don’t think it has effected the heating costs at all. Though yes with the heater on it costs to run. its 500w so can be 12kwh per day so depends what you pay. Our heater isn’t on 24×7 and is set it, I think, 14’….
      From our elec usage it only runs the heater constantly in the cold months. If your fan is too fast….
      Though even at 1.50/day over winter, its cheaper than fixing mould everywhere… A price we are happy to pay
      See link at top of page as I have a better list of info to reduce moisture/condensation. If those addressed maybe your landlord could turn speed down a notch?
      Ours feels nothing like an open window. And an open window didn’t work either! In fact our bedroom windows stay closed now whereas before we had to have them open and still got condensation. Our bedroom deffo warmer now!
      Good luck!

  22. Hi !

    I am a landlady , it’s a 4 bed semi detached house , we bought it about 6 months ago , it was a total rack and we done full refurbished , and rented the house , this was the first proper winter for a tenant , condensation appeared on one of the bedroom , and tenant moaning about the mould , she also said she is out most of the time and when she is back , heating they put it on for a full speed , which obviously cause more condensation , we have fitted extractor fan in kitchen – which I doubt that it’s being used , and have a small mould growth in pantry. And in one of the big bedroom there is a lot of condensation on window My question is , do you think this product will help me to sort out this issue and most importantly as tenants don’t like to pay big electricity bill to pay – and she switched that off than condensation problem would be still there ? Or can we adjust the settings that she can’t manipulate it ,( I assume that it will go in loft and the ceiling in landings are quite high anyways) thanks ,

    1. Yes it will help! We have installed an enviro vent system in one of our rentals. Tenants were drying clothes and not using the fan as it was always switched off. This unit has dried out the bungalow completely. Been installed for 2 years. I will be fitting the nuaire unit above in our holiday home shortly, same idea but lots cheaper than envirovent system.
      If and when you have it fitted don’t tell the tenants how to turn it off though!

  23. Hi
    I have just had a nuaire drimaster Heat fitted this week. The heater has been connected seperately to the fan so I can switch it on or off when I like. My question is is there anyway you can tell the heater bit is working when I switch it on, I cannot feel any heat.

  24. We live in a detached 3 bed house near the coast and get a lot of condensation and black mould. I am considering the nuaire system but have 2 questions…..
    1, Should I get the heater? Some comments make me think it will be very expensive to run as we live in a cold area (wild Northern Ireland coast!) though it is seldom cold enough for snow to settle.
    2, My landing is very small, basically just as wide as the stairs (800mm) with all three bedroom doors leading direct off the top step, so just a small 800mm sq space. Will the vent work there as the installation says leave at least 400mm around the vent for setting 3.

    Help! and thanks!

  25. Hello, I’m interested in the PIV but am wondering how it might work for me. I have a Dormer Bungalow with two bedrooms upstairs at the same height as the loft. Would these bedrooms benefit from PIV as the unit would be at the floor level of the first floor pushing air downwards. I am not really able to install it any higher as there is nothing between the ceilings and roof.

  26. Interesting and helpful read. Going to be installing a pic soon. JG having read the installationinstructions on a couple of different units , they say to seal all possible leaks in ceiling. Has I have downright in all rooms do they need to be sealed some how.


    1. I’d not overly worry about downlighters to be honest. You jut don’t want gaping holes. We have downlighters in the bedroom, bit (non closing) extractor vent in bathroom – and it works a treat

  27. I have a problem in a large downstairs flat roofed bedroom/En suite extension at back of house mainly with a foisty smell on clothes in wardrobe and dank smell on towels in the En suite so would a drimaster unit in the loft(which is quite a way from problem site) be of any help? There is no condensation mould or anything like that but feel there is an airflow problem in this large low extension. Would be grateful for any advise.

    1. Hi Jan
      I am no expert, but what you describe sounds like high humidity. Id say buy a handful of the cheap humidity meters and place them in various locations, good places and bad places, and compare. If you have high humidity in the smelly areas and low elsewhere, then could be moist air. A drimaster woukd help move the damp air. However, see top of this page t o my PIV specialist site, and it gives more advixe. eg hints to get damp air away – eg MUCH BETTER fan to get air out of the ensute (shower?). So Id GUESS at checking humidity, then finding sources of nmoisture and removing thenm, and drimaster only if improved extraction and ventilation does not help

      1. I have condensation in bay windows but also in bedroom in wardrobes with sliding doors—We do not have loft space–as loft is boarded–would Flatmaster help? how do I find an installer in Harrow Middx are?

  28. I have my loft have had floorboards and carpeted. However the loft space is not loving dpace (i use for storage). Its a 1900 property i think …solid cold walls. A company i have contacted thinks they can still install this in the following way..
    1) to have it fitted as normall but i will have to take a bit of carpet off and remove a bot of floorboard
    2) it must then be ducted to an existing vent on the loft roof to fetch the external air

    my landing space is already very freezing …will the heater element bring in watm air? i cant have it any colder!

    we have wet windows and also very cold external ealls which attract wet mold

    1. I am no expert, but their plan sounds logical but you would lose out on solar heat gain when the “loft” usually gets warmer than the outside when the sun is shining on it.
      The heater will help – you can turn the thermometer down so it cuts in earlier. Do remember its not blowing out like a fan heater, its just a gentle air movement. But if you don’t want it any colder, the heater model will be better.
      Please see my other site (link at top of page) that talks about these, as PIV is one part of the solution – if you can prevent moist air (damp, shower/kitchen extraction, not drying clothes inside netc) that halps, and PIV is just the final icing.

      1. Hi I have had a flatmaster 2000 fitted today unfortunately I had a hospital appointment and was unable to speak with the installers, my question is – is the red button on the outside of the unit an off/on switch, also how do I turn on the heater part of the machine as the air seems to be very cold and there doesn’t seem to be anything on the outside of the machine like a heater switch, I had thought it would have a heater and a thermostat to regulate the heat ….thanks for any help you can give me

        1. Hi Meg,

          The big red switch is the manual control for the heater on the Flatmaster 2000 left and right handed models. This triggers the intergral heater on and off.

          Kind regards,


  29. Hi,

    This may be what I’ve been looking for. We suffer from terrible condensation issues in one of our bedrooms which has inward opening double glazed patio doors as a form of Juliette balcony.

    I’ve purchased a Karcher window vac to remove the condensation as over 4 panes of nearly 1.5 m high glass it can take a while. We sleep with a window in the room ajar to reduce condensation (which helps), we shower with windows open and a continuous ventilation system operating. I don’t think the insulation in our loft helps as it isn’t that thick and thus hot air easily escapes.

    Can the drimaster be installed in the eaves of the loft which has been transformed into living space? At each side of the loft room are access hatches which allow for crawling along the beams.

    1. Hi
      See link at top of this page for more info.
      As I understand it, the drimaster needs to be able to suck in external air and push it into the house . So, you should not install in the living space as that would be sucking in “internal” air that already is moist. But having it in the eves in the side of the loft sucking air from there should be OK. You need the unit installed where there is fresh dry air available

  30. than yu for your advice i will look at this product and hope fully get rid of the mould and bad air in my basement

    1. Hi. See link at top of this page for more info. The PIV is good for refreshing air and preventing mould and condensation caused by moist internal air. You mention basement – if you are getting DAMP walls from moisture getting in from outside it will not help with the mould – it does not fix damp. If walls are cold and get condensation on from internal moist air condensating that in will help. But make sure its not damp otherwise you are fixing the wrong problem

  31. Hi. We have just installed an Envirovent system (which may not have been the most cost effective solution now reading these blogs). The issue we are having I’m guessing would be the same with either PIV system. On installation it was set to medium, the house became extremely cold, we don’t have gas central heating but energy efficient electric radiators which maintain a lower economic temperature during the day to keep heating costs down when heating the room to 21deg in the evening. As the Envirovent unit heats the air from the loft to 10degC and circulating this around the house, the radiators in some rooms downstairs are constantly giving out heat – this is going to cost us significantly in electricity. We have now reduced the daytime setting on our heating system, but the house is constantly very cold. Any advice most welcome. Thanks

    1. I changed our “heater” to a higher temp, was a few years ago, maybe 14-16′. And I accept (and say on the linked site) the elec bill goes up over winter. However the extra elec bill vs. mould/damp/wet walls/painting etc is much cheaper!
      Our landing is cooler, but no way does it cool downstairs! (also, apparently, its a myth to keep heating on all day thinking its cheaper than warming from cold – so research that – even MoneySavingExpert did an article).
      So maybe your fan speed is too high? Ours is only set on 1/2 possible power. Getting the setting “right” took a few goes as it is a balance. Maybe EnviroVent just stuck it on high to get results without considering.
      Also, as the air is less humid, for us, we feel warmer for a lower temperature – so, say, if 23′ was the right temp before, we now have 21′. Also, as we no longer have windows open to clear condensation, we don’t lose heat that way.
      Its all a compromise, but perhaps check/tune settings (assuming the EV unit can be adjusted)

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